The present invention relates to a communication interface unit, a connection tool, a wrap tool, and a wrap testing method, more particularly to a communication interface unit provided with such a communication interface as SCSI, RS232C, etc. used for a computer, as well as a connection tool, a wrap tool, and a wrap testing method for testing the communication interface unit respectively.
Various types of communication interfaces have been put into practical use so as to exchange information with peripheral devices for expanding the functions of computers. SCSI (Small Computer System Interface) is one of such well-known interfaces. The use of such a SCSI interface enables a plurality of such peripheral devices as a hard disk drive, a printer, etc. to be connected to a computer in a so-called daisy-chain connection manner.
A device that uses such a communication interface as the SCSI, etc. (hereafter, to be referred to as a communication interface unit. Especially, a device that uses the SCSI is referred to as a SCSI device) must be checked beforehand for the operation and connections of signal lines. For example, a wrap test is conducted for the object SCSI device by entering an input signal and outputting an output signal separately. Concretely, in the case of such a wrap test, an output signal from the SCSI device is wrapped to the SCSI device as an input signal as is.
In such a wrap test that tests the operation and connections of signal lines of the object SCSI device, a connection tool referred to as a wrap tool is employed. In this wrap tool, each terminal is shorted with another so as to wrap mainly a SCSI input signal as an output signal as is. Such a testing technique is disclosed in Published Unexamined Patent Application No. 5-73445. The technique checks connections of SCSI signal lines for normal or abnormal. The wrap tool is composed simply as described above, so the outside configuration of the wrap tool is similar to that of a terminal connector, that is, the so-called SCSI terminator attached to the end of the daisy-chained SCSI devices.
However, because of the similarity of the outside configuration between the wrap tool and the SCSI terminator, problems often occur in wrap tests for SCSI devices with use of this wrap tool; a SCSI terminator is often taken instead of a wrap tool by mistake, so that the test result becomes wrong or this wrap tool is left at the SCSI device even after the wrap test, thereby causing the SCSI device to malfunction.
In order to solve this problem, there is a technique proposed for checking two SCSI control printed board unit connectors connected to each other via cable in a SCSI device (refer to Published Unexamined Patent Application No. 63-229550). This technique checks exchanges of signals between two SCSI control printed board units in which each SCSI terminal is connected to another, thereby enabling those two SCSI control printed board units to be tested.
If a wrap test is conducted as conventionally for two SCSI device connectors connected to each other via a cable, that is, each terminal is connected to another between those two SCSI connectors used as a wrap tool, however, two SCSI devices are required. It is impossible to test only one of the SCSI devices in this case.
Generally, a SCSI device is often provided with two connectors so as to enable data exchanges with external devices connected to each other in a daisy-chain manner as described above. These two connectors are connected to common signal lines from a SCSI controller provided in the SCSI device. Consequently, the above-mentioned wrap test must be conducted for all the connectors of the SCSI device.
In this case, although a wrap test is possible with use of a conventional wrap tool formed by connecting the terminals to each other between SCSI connectors via a cable, a problem arises; the object SCSI device is determined to be normal in a wrap test conducted only at one connector in some cases with use of a wrap tool whose outside configuration is similar to that of the SCSI terminator. In such a case, another problem might also arise; the wrap tool is left at the SCSI device by mistake even after the wrap test, thereby causing the SCSI device to malfunction in the started-up operation.
Under such circumstances, it is an object of the present invention to provide a communication interface unit, a connection tool, a wrap tool, and a wrap testing method that can test the operation of the communication interface unit used for a computer in a simple configuration respectively.
The communication interface unit of the present invention includes controlling means for controlling a plurality of I/O signals, thereby controlling the object communication interface unit. A plurality of the I/O signals include an acknowledge signal so as to test the operation and connections of the signal lines of the communication interface unit used for a computer. The controlling means outputs this acknowledge signal and receives the output acknowledge signal, thereby detecting the acknowledge signal. The acknowledge signal may be a constant voltage supply power from a power supply unit. In this case, the acknowledge signal can be detected by checking whether or not the input side reaches a constant voltage level.
Furthermore, the communication interface unit includes separating means and a plurality of relaying means. Separating means is provided with a plurality of signal lines for transferring a plurality of I/O signals of the controlling means. An output signal line for outputting the acknowledge signal and an acknowledge signal line for receiving the acknowledge signal, that is, the acknowledge signal line for letting the controlling means detect the acknowledge signal are also included in those I/O signal lines. Each of those signal lines is further separated into a plurality of signal lines, thereby forming a plurality of signal line groups corresponding to a plurality of I/O signal groups of the controlling means. Potential dropping means is added to each of the separated acknowledge signal lines. Each potential dropping means has resistors, which may be connected serially at middle points of the acknowledge signal line. And, such relaying means as a connector or the like is connected to each of the signal line groups of the separating means so as to relay signals to an external device.
The acknowledge signal is transferred through each of the output signal lines separated by separating means. In a wrap test, this acknowledge signal is output, then wrapped as an input signal. Concretely, the acknowledge signal is wrapped and transferred through each of the acknowledge signal lines. As described above, because potential dropping means is added to each acknowledge signal line, the potential of the acknowledge signal drops. Each signal line, separated by separating means, comes to have a connection point. Consequently, two relaying means are composed so that an output signal line of one relaying means is connected to an acknowledge signal line of the other relaying means and an acknowledge signal line of one relaying means is connected to an output signal line of the other relaying means. Concretely, an acknowledge signal line and an output signal line are connected mutually and this state is equivalent to a parallel connection of the potential dropping means. The potential is thus stabilized in correspondence to the number of added potential dropping means. This is why it can be determined whether or not the object connection is done for a wrap test by determining whether or not the object potential is stabilized in accordance with the number of added potential dropping means. And, if a wrap tool whose outside configuration is similar to that of the SCSI terminator is used for a wrap test of a SCSI device, wrong wrap tests can be prevented. This is because only one of potential dropping means is operated so that the remaining potential dropping means are excluded from the test.
The potential dropping means may be an element such as a resistor or the like for dropping the potential of the signal or for raising the potential. In other words, the potential dropping means may be any one that can stabilize the potential in accordance with the number of added potential dropping means.
The connection tool of the present invention used for wrap tests is connected to at least two relaying means included in the above communication interface unit. This connection tool is provided with connecting means for connecting a first terminal to be connected to an input signal line of the first signal line group separated by the separating means and a second terminal to be connected to an output signal line of the second signal line group. Consequently, as described above, two relaying means are composed so that an output signal line of one relaying means is connected to an acknowledge signal line of the other relaying means and an acknowledge signal line of one relaying means is connected to an output signal line of the other relaying means. Potential dropping means are thus connected in parallel. Consequently, it can be determined whether or not a connection is done for a wrap test by determining whether or not it is detected that the potential of the object acknowledge signal is stabilized in accordance with the number of added potential dropping means.
The above connecting means should preferably be connected to a plurality of relaying means provided in the communication interface unit. To meet this requirement, therefore, the first connecting means including the first terminal and to be connected to the first relaying means connected to an input signal line of the first signal line group and the second connecting means including the second terminal and to be connected to the second relaying means connected to an output signal line of the second signal line group are formed independently of each other. The first connecting means and the second connecting means formed as described above respectively are relayed mutually via a connection cable. This makes it easier, for example, to determine a difference between two devices connected to a connection cable whose both ends are connected to a connector respectively so as to be distinguished from a SCSI terminator in physical outside configuration. It is thus avoided to use a wrap tool whose outside configuration is similar to that of the SCSI terminator.
In the above case, potential dropping means is added to each of the acknowledge signal lines separated by separating means provided in the communication interface unit. However, the potential dropping means, which is requested only to drop the potential of the corresponding acknowledge signal, may be provided outside the communication interface unit. The connection tool of the present invention is therefore provided with controlling means for outputting an acknowledge signal and receiving the acknowledge signal so as to test the operation of the communication interface unit used for a computer and controlling a plurality of I/O signals including the acknowledge signal, thereby controlling the communication interface unit; separating means provided with a plurality of signal lines for transferring a plurality of the I/O signals of the controlling means, a plurality of the signal lines including an output signal line for outputting the acknowledge signal and an acknowledge signal line for receiving the acknowledge signal, the separating means being used for separating each of a plurality of the signal lines into a plurality of signal lines, thereby forming a plurality of signal line groups corresponding to a plurality of I/O signals of the controlling means; and a plurality of relaying means for relaying each of the signal line groups of separating means to an external device. Consequently, the connection tool of the present invention for testing the communication interface unit is only needed to add the following connection tool. Concretely, the connection tool is provided with a first connector attached to one of the two relaying means and provided with a first terminal to be connected to an input signal line of the first signal line group separated by the separating means and a second connector attached to the other relaying means and provided with a second terminal to be connected to an output signal line of the second signal line group, as well as a specific connecting means for connecting the first terminal of the first connector to the second terminal of the second connector with potential dropping means therebetween.
Furthermore, the wrap tool of the present invention used for testing the above communication interface unit comprises controlling means for outputting an acknowledge signal and receiving the acknowledge signal so as to test the operation of the communication interface unit used for a computer and controlling a plurality of I/O signals including the acknowledge signal, thereby controlling the communication interface unit; separating means provided with a plurality of signal lines for transferring a plurality of the I/O signals of the controlling means, a plurality of the signals including an output signal line for outputting the acknowledge signal and an acknowledge signal line for receiving the acknowledge signal and separating each of the signal lines into a plurality of signal lines, thereby forming a plurality of signal line groups corresponding to the I/O signals of the controlling means; potential dropping means being added to each of the separated acknowledge signal lines; a plurality of relaying means for relaying each of the signal line groups of separating means to an external device; and connecting means for connecting the first terminal to be connected to an input signal line of the first signal line group separated by the separating means and the second terminal to be connected to an output signal line of the said second signal line group to at least two of the relaying means serially.
This connecting means forms the first connecting means including the first terminal and to be connected to the first relaying means connected to an input signal line of the first signal line group and the second connecting means including the second terminal and to be connected to the second relaying means connected to an output signal line of the second signal line group independently of each other. The connecting means is provided with a connection cable for relaying the formed first connecting means to the formed second connecting means.
The wrap testing method of the present invention for the above communication interface unit comprises the step of outputting an acknowledge signal and receiving the acknowledge signal so as to test the operation of the communication interface unit used for a computer and controlling a plurality of I/O signals including the acknowledge signal, thereby controlling the communication interface unit; separating each of signal lines for transferring a plurality of the I/O signals, a plurality of the signal lines including an output signal line for outputting the acknowledge signal and an acknowledge signal line for receiving the acknowledge signal into a plurality of signal lines, thereby forming a plurality of signal line groups; connecting the acknowledge signal transferred through an input signal line of the separated first signal line group to an acknowledge signal line of the second signal line group; and dropping the potential of each acknowledge signal transferred through the acknowledge signal line so as to achieve the object of the present invention.